BRPI0610255A2 - bone anchor for attaching a fixture to a bone and vertebra, combination of bone anchor and fixture to retain adjacent vertebrae, and method of mounting a bone anchor - Google Patents

Abstract

BONE ANCHOR FOR ATTACHING A FIXATION ELEMENT TO A BONE AND A VERTEBRA, COMBINATION OF BONE ANCHOR AND FIXATION ELEMENT TO HOLD ADJUSTABLE VEGETABLES TO EACH OTHER, AND, METHOD OF ASSEMBLY OF A BONE ANCHOR. A bone anchor for attaching a shaft to a bone having a bone anchor member for attachment to the bone and an anchor head having a U-shaped opening for receiving the shaft is described. The bone anchor also includes a locking cap that has a main body and an adjusting screw. Advantageously, in one embodiment, the locking cap is preferably designed such that a single tool can be used to lock the locking cap in place on the anchor body, preferably with a 90 ° turn, and then preferably by actuating. adjusting screw to secure the rod. The locking cap also preferably non-threadably engages the anchor body. The anchor body preferably has an inclined surface on its upper surface that elastically deflects extension flaps on the main body to secure the locking cap to the anchor body. Also described is a method of implanting and assembling the bone anchor.

Description

"BONE ANCHOR FOR ATTACHING A FIXATION ELEMENT TO A BONE AND A VERTEB, COMBINATION OF A BONE ANCHOR AND FIXATION ELEMENT TO HOLD ANOTHER, AND A BONE ANCHOR ASSEMBLY METHOD"

BACKGROUND OF THE INVENTION

This invention relates to bone fixation devices and related fixation methods. More specifically, this invention relates to bone anchors, such as spinal fixation screws and hooks, including polyaxial bone anchors, and related methods of spinal fixation.

TECHNICAL FIELD OF THE INVENTION

Many methods of treating spinal disorders are known in technology. A known method involves anchoring a screw or hook to the vertebrae, and attaching the screws or hooks along a spinal rod to position or immobilize the vertebrae relative to one another.

Bolts or hooks usually have U-shaped channel heads into which the spinal rod is inserted and subsequently secured by an adjusting screw or other fastener or locking cap. This method can usually involve multiple screws or hooks as well as multiple spinal rods. With this method, the spinal stem (s) can be modeled so as to keep the vertebrae in an orientation such as to correct close spinal disorder (for example, straighten a spine that has abnormal curvature). Additionally, or alternatively, the screws or hooks may be spaced along the rod (s) to compress or distend adjacent vertebrae.

Surgeons have often encountered considerable difficulty with this method because of the complicated alignment of the spinal rod (s) with the U-shaped channels in the screw heads or hooks, for example, the screw heads or hooks are generally out of place. alignment with each other because of the curvature of the spine or the size and shape of each vertebra. In order to facilitate the insertion of the spinal rods into the U-shaped channels, and to provide additional flexibility in the positioning of the spinal rods and screws and hooks, screws and hooks have been developed in which the head (including the U-shaped channel) initially pivots in to the anchor member (for example, spike or bolt hook). An example of such a screw is disclosed in United States Patent 5,586,984 to Errico etai. which is incorporated herein by reference.

The process of positioning and adjusting known bone anchors can be tedious and relatively time consuming, typically requiring more than one surgical tool to hold the spinal rod and anchor member in desired positions. Even with a high degree of skill and care, the process of positioning an adjusting screw has known another fastener on the bone anchor and then manipulating the screw or fastener to secure or re-attach the spinal stem and anchor limb may take longer. than desired during a surgical procedure, or even cause the rod, anchor member or both to move out of position before the attachment is completed.

Therefore, there is still a need for bone anchors including polyaxial bone anchors that provide a mechanism for securing the spinal shaft and anchor member in their desired positions.

SUMMARY OF THE INVENTION

The invention is directed to a bone anchor including a polyaxial or monoaxial bone anchor for attaching a stem, such as a spinal shaft or other device, to a bone such as a vertebra. Bone anchor may include an anchor limb (such as a screw, hook, or similar structure) for attachment to the bone and a bone anchor anchor head. The anchor head may be integral with the anchor member or may be a separate part or component that engages with the anchor member, and may rotate polyaxially around it. The anchor head preferably has U-shaped openings for receiving the rod. End of the anchor may have a recess for receiving the head of the anchor member such that the anchor member may initially angularly rotate polyaxially with respect to the anchor head. The bone-axial anchor may also include a locking cap capable of securing the shaft and anchor member in the desired positions.

The locking cap advantageously simplifies and preferably reduces the fastening process. The locking cover preferably includes a main body, an adjusting screw and a saddle.

The adjusting screw is preferably preloaded into the main body so that upon application of a torque, preferably below a predetermined value, for example about 4.5 Newton-meters, the main body rotates with the adjusting screw. Preferably, the saddle contacts or is coupled to the adjusting screw. Typically, after the anchor member is implanted into a bone and a rod is inserted into the bone anchor, the locking cap is positioned above the anchor head, where the main body features snap into the head features to allow the locking cap to preferably lock into the bone. place at the anchor head, preferably with a turn of 90 ° or less.

The instrument preferably engages the adjusting screw and applying a rotary movement in one direction to lock the body cap (anchor head) also rotates the main body so that the main body engages the bone anchor. Once the anchor rod and member are aligned in the desired manner, the adjusting screw can then be twisted into the anchor head, which causes the saddle to snap into place and then lock the rod in place. As a result, the fixation of the rod may cause the anchor member in a bone-axial anchor to be locked in place. Alternatively, the anchor member may be locked to the anchor head in a polyaxial bone anchor regardless of whether the nail is attached to the bone anchor. Advantageously, main body and adjusting screw features allow the same tool to be used in a single action to position and lock the main body to the anchor head and then turn the adjusting screw.

A bone anchor for attaching a fixture to a bone according to one embodiment includes an anchor member (e.g., a bone screw) for attaching to said bone; a body having an upper part and a lower part, the body coupled to said anchor member near said lower part, the body forming a hollow interior and having a general U-shaped channel in said upper part for receiving said fastener; and a locking cap mounted removably and unthreaded on said upper part of said anchor head, said locking cap may have a main body (sometimes referred to as a retaining ring) and a threadedly attached adjusting screw in said body to attach and secure the defixing element to the body. The main body of the locking cap may have one or more resiliently deflectable tabs and the body may have an inclined surface on its upper surface, wherein the flap deflects on the inclined surface of the body by rotating the main body relative to the body.

The main body and adjusting screw may be preloaded such that rotation of the adjusting screw causes the main body to rotate. The adjusting screw may be preloaded with the main body such that a force of about 2 to about 6 Newton-meters is required to allow the adjusting screw to rotate relative to the main body. The main body and adjusting screw may be driven by a single instrument that fits only said adjusting screw until said main body is locked in place in said housing.

The body may additionally include a limiting surface on its upper surface to resist removal of the main body from the body. The upper body surface may additionally have a retaining surface, and the limiting surface of the retaining surface may form a recess for retaining the main body flap. The main body may rotate about 90 ° or less relative to the body to secure the main body to the body. The main body of the locking cap may include one or more dovetail projections and wherein the housing comprises at least one dovetail notch at the top.

When the main body is attached to the body, the dovetail projection is received on the dovetail to prevent expansion, but the dovetail connection in some embodiments may not provide a force on the body during rotation of the main body. The locking cap may additionally include a saddle coupled to the adjusting screw and independently rotatable relative to the adjusting screw return.

The bone anchor may optionally include a compressible mandrel which has a lower surface supporting a lower flange in the lower body region. The mandrel may have an extended shoulder that rests on the lower body flange. The bone anchor may additionally optionally include a sleeve with an inner recess receiving the mandrel and having a tapered inner surface to provide a compressive force on the mandrel's outer conical surface by moving the sleeve toward the lower body to lock the anchor member. The jacket preferably has a channel for receiving the fastener and the channel has at least a portion which has an opening smaller than the deflection member so that the fastener is snap fit into the jacket.

The liner channel has an opening and the liner additionally has an upper surface which has a slanted surface that interacts with the lower surface of the locking lid to widen the liner opening. The body may have a mounting notch and the mandrel may have an extended shoulder. wherein the mounting notch is configured to allow a lower mandrel opening to expand to receive the anchor member head upon receipt of the extended shoulder.

A bone anchor for attaching a vertebrae fastener according to another embodiment comprises an anchor member for attachment to said vertebrae; the body having an upper part and a lower part, the body forming a generally tubular member having an inner cavity, an upper opening in the upper part which communicates with the inner cavity and a lower opening in the lower part which communicates with the inner cavity, the part upper wall having an end wall, at least one notch and a channel for receiving the deflection member, and the end wall has one or more recesses formed by a sloping surface and a straight wall, the slanted surface being inclined to the end wall and the straight wall being substantially perpendicular to the end wall; and a locking cap removably mounted to the upper body, the locking cap comprising a locking ring and a set screw threadedly attached to the locking ring, the locking ring comprising one or more deflectable tabs and one or more projections. , the flexible frame configured and adapted to interact with a small cavity to deflect as the clamping ring is rotated relative to the body and the projection configured and adapted to be received in its respective direction by rotation of the clamping ring.

The end wall may additionally include a bearing surface, the bearing surface and the straight surface forming a recess for deflecting the flap by rotating the clamping ring approximately 90. The projection is swallowtail shaped and the notch is swallowtail shaped , and wherein the respective dovetail shapes are adapted and configured so as not to provide engaging forces as the dovetail projection is received in the dovetail projection, but the interaction of the projection and the notch may prevent the part expand beyond a predetermined distance.

The bone anchor may comprise a liner having a U-shaped channel adapted and configured to receive the deflection member, retaining tabs and a lower portion having an internally conical surface; and a compressible mandrel having an externally tapered surface, a hollow interior for receiving a portion of the anchor member, a lower aperture, a plurality of flexible extensions and a shoulder extending beyond the outer surface, the lower aperture of the mandrel configured and adapted thereto. a natural state to be smaller than apart from the anchor member received within the mandrel and having an expanded state allowing at least a portion of the anchor member to move therethrough; wherein the body comprises a flange near the bottom aperture, a bottom mounting notch, and sleeve retaining slots, the body containing the mandrel near the flange and the internally tapered surface of the sleeve contacting the outer surface of the mandrel; whereby the translational movement of the shirt within the body compresses the resilient extensions of the mandrel inwardly to secure the anchor member relative to the head without the mandrel offering a translational motion. The anchor member may be adapted and configured to be inserted into the body by the lower opening, and the mandrel may be adapted and configured to be inserted into the body by the upper body openings, but not by the lower opening, and wherein the anchor member may be inserted into the body. mandrel only when the mandrel shoulder is received in the mounting notch. The jacket retaining tabs may be positioned in slots formed in the body. Slots and retaining tabs may be configured and adapted to align the sleeve securing member channel with the body retainer channel.

A method of fabricating a bone anchor for a spinal fixation device that receives a fixation element may include the steps of providing an anchor member having a bone engaging portion and a head; providing a body having an upper opening, a lower opening, an inner cavity communicating with the upper and lower openings, a channel for receiving the fastener and a mounting notch, the lower opening being smaller than the upper opening; providing a mandrel having a lower aperture communicating with an inner cavity, and a shoulder near the lower aperture, the inner mandrel cavity being configured to receive at least a portion of the anchor member head and the lower aperture being smaller than at least a portion of the anchor limb head; insert the head of the anchor into the lower opening of the body; align the spindle shoulder with the body mounting notch; inserting the head of the anchor member lower opening of the mandrel while the mandrel is located in the inner cavity of the body and the shoulder is aligned with the mounting notch so that the mandrel expands and the shoulder is received in the mounting notch; forming a mandrel and anchor member assembly, allowing the mandrel to retract so that the shoulder moves outward from the mounting member and the anchor member head is retained by the mandrel; Reposition the arbor and anchor member assembly so that the shoulder does not align with the mounting notch. The assembly method may further comprise providing a jacket having an internally conical surface, retaining tabs and a channel for receiving the fastener; inserting the liner into the inner cavity of the body through the upper opening; and positioning the liner so that at least a portion of the internally tapered surface overlaps at least a portion of the outer surface of the mandrel and that the retaining tabs fit snugly into the slots formed in the body after the anchor member and mandrel assembly is formed in the body.

The method of fixation of vertebrae in the spine using a first bone anchor that has a first anchor member and a first anchor head that has a first opening or receiving channel of the shaft, and a second polyaxial bone anchor that has a second anchor member and a second anchor. Anchor head having a second or channel receiving rod opening is also described. The method may include inserting the first anchor member into a first vertebra and inserting the second anchor member into a second vertebra.

The first anchor member may be inserted into a lateral mass of a first vertebra, and the second anchor member may be inserted into a lateral mass of a second vertebra. As an example, at least one of the first and second vertebrae may preferably be selected from the group of vertebrae comprising the lumbar or thoracic regions of the spine, although other areas of the spine are contemplated.

After the bone anchor is inserted into the bone, a stem may be inserted into the stem receiving channel above the bone anchor. The locking cap can then be placed over the rotated bone anchor 900 or less to engage the locking cap with the bone anchor and, in particular, a main body of the locking cap engaging the bone anchor anchor head. With the locking cap in this position, the stem is positioned in the receiving channel of the bone anchor stem and may undergo translational and / or rotational movement in the stem receiving channel. Using the same tool that was used to twist the main body to fit the main body to the anchor head, the adjusting screw can then be rotated by applying a predetermined torque to the adjusting screw so that the adjusting screw can rotate independently of the main body. Continuously rotating the adjusting screw holds the rod in position, and may additionally lock the position of the anchor head or body to the anchor member, which may be, for example, a screw or hook. Alternatively, with the locking cap fitted and covering From the opening of the anchor body, the position of the anchor head on the anchor member can be secured and fixed, although the spinal shaft may rotate or translate in the receiving channel of the stem.

The method may also include attaching the stem to a bone anchor, locking the main body to the anchor head, positioning the stem relative to one or both bone anchors, rotating or translating the stem into one or more of the stem receiving channels, and securing the stem. rod into one or more bone anchors, for example, by turning the adjusting screw of a respective bone anchor.

The method may additionally include loosening the adjusting screw so that the stem can move relative to the bone anchor, for example, turning the adjusting screw in an opposite direction, or second direction, repositioning the stem into one or more stem receiving channels. , and / or repositioning the anchor head relative to the anchor member of one or more bone anchors, and locking / securing the rod in position and / locking / securing the anchor member relative to the anchor head.

The method may further include rotating the locking cap in an opposite direction, or second direction, in order to swing or remove the bone anchor locking cap and, more particularly, turning the main body in an opposite direction, or second direction, to lock and lock. , if desired, remove the bone anchor locking cap.

The main body can be rotated using the same first tool used to couple the main body to the anchor head and tighten the adjusting bolt, or alternatively a second tool can be used to swivel the main body, or alternatively both the first and the second. The tool can be used to swing the main body on the anchor head.

BRIEF DESCRIPTION OF DRAWINGS

The detailed description will be better understood in conjunction with the accompanying drawings, where like reference characters represent like elements, as follows:

Figures 1-6 are perspective, front, side, front cross-sectional views (taken along line AA of Figure 6), side cross-sectional views (taken along line BB of Figure 6) and respectively a top view. illustrative embodiment of a bone-axial anchor according to the invention;

Figure 7 is a front cross-sectional view (taken along line A-A of Figure 6) of the anchor head and polyaxial bone anchor locking cap of Figures 1-6;

Figure 7A is a perspective view of the anchor head without the locking cap;

Figures 7B1-5 are front, side, top, and cross-sectional partial cross-sectional views, respectively, of one embodiment of a shirt showing representative dimensions;

Figure 8 is a perspective view of one embodiment of a slotted mandrel according to the invention;

Figure 9 is a perspective view of the main body of a locking cap according to the invention;

Figure 10 is a perspective view of a locking cap adjusting screw according to the invention;

Figure 11 is a perspective view of the saddle of a locking cap according to the invention;

Figures 12-15 are top, cross-sectional views (taken along line AA of Figure 12), cross-sectional views (taken along line BB of Figure 12) and enlarged partial sectional view, respectively, of the saddle of Figure 11 showing representative dimensions;

Figures 16-21 are perspective, top, front, front cross-sectional views (taken along line AA of Figure 17), side, and side cross-sectional views (taken along line BB of Figure 17), respectively; locking cap mounted comprising the components of figures 9-11;

Figures 22-26 are top, cross-sectional front perspective views (taken along line AA of Figure 23), and two enlarged partial cross-sectional views, respectively, of the bone-axial anchor with the locking cap inserted and in an open position. not docked or uncoupled and with the stem unlocked;

Fig. 27 is a top view of the locking cap inserted and in an open position on the anchor head;

Figures 28-32 are perspective cross-sectional views of the front cross-sectional view (taken along line AA of Figure 29) and two enlarged cross-sectional views, respectively, of the polyaxial bone anchor with the locking cap inserted and in a closed, engaged position coupled, and with the stem unlocked;

Figure 33 is a top view of the locking cap inserted and in a closed position on the anchor head;

Figures 34-38 are perspective top, cross-sectional front views (taken along line AA of Figure 35) and two enlarged partial cross-sectional views, respectively, of the bone-axial anchor with the locking cap inserted and in a closed position; engaged or coupled, and with the rod locked; and

Figures 39 and 40 are perspective views of illustrative embodiments of a monoaxial bone anchor and a spine hook engaging a locking cap.

DETAILED DESCRIPTION OF THE INVENTION

Although a bone anchor will be illustrated and described with reference to certain preferred or exemplary embodiments, the invention should not be limited to such preferred or exemplary embodiments. In addition, the features described and illustrated herein may be used singly or in combination with other features and embodiments.

Figures 1-6 show one embodiment of a bone-axial anchor. The polyaxial bone anchor 100 includes a locking cap 102 (not shown in figures 2-5), an anchor head 104, and an anchor member 106. The bone anchor 100 may also be a bone-axial anchor such that the Anchor and anchor head are integral members that are fixed to each other. (See figure 39). The end anchor 104 (sometimes referred to as body technology) has a general U 101 opening for receiving a spinal rod 108 (note that spinal rod 108 is not shown in Figs. 2-6) or another device such as, for example. , a plate. Anchor member 106, which may be a bone screw, hook or other similar structure, is coupled to the head of anchor 104 such that it may preferably rotate axially relative to head 104. In one embodiment of the invention, anchor member 106 may rotate. angularly about axis 107 at an angle θ is preferably at least about 25 ° in any direction (i.e., the angular rotation of the anchor member 106 forms a 50 ° fence cone), although other angulation bands are contemplated. One or more polyaxial bone anchors 100 may be attached to, for example, the vertebrae via respective anchor members 106, and a spinal rod 108 or other device may be inserted into the U-shaped openings 101 and then locked to properly align the spine or treat As shown in Figures 7 and 7A, the anchor head104 includes a generally cylindrical hollow housing 710 and may optionally contain a U-shaped sleeve 612, and an arbor 814. The housing 710 has a non-inner walled region. generally cylindrical conical 711a, b, but alternatively may have at least some wall regions that are inwardly conical toward the anchor member 106. The outer shape of housing 104 may be generally cylindrical and may have conical or straight wall regions. Other exterior shapes for housing 104 are also possible. The jacket 612 has retaining tabs 613a, b snap-fitting into respective slots 715a, b opposite walls of housing 710 as the jacket 612 is preferably inserted downwardly into housing 710. In one embodiment of the invention, slots 715a , b are sized to allow the jacket 612 to move up and down about 1.5 mm, although other distances are contemplated. One or more slots may be formed in housing 710, depending on the number of retaining tabs. There may be more formed slots than retaining tabs. In addition, the slots may extend or be formed across the width or circumference of the interior housing wall so that the jacket may rotate (rotate) in the housing or the slots may be formed to be approximately the same width as the tabs so that the jacket cannot rotate (spin) on the body. The configuration and interaction of the retaining tabs on the liner or slots may be designed so that the liner is flush with the body or that no self-aligning features are provided. In this manner, the retaining tabs may interact with the slots to align the channel retainer channel with the body retainer channel. The retaining tabs and slots may be reversed so that the tabs may be formed in the housing and the slots may be formed in the jacket. Anchor head 104 has an upper part 114 and a lower part 118 and a hole 116 extending along the longitudinal axis 107. An upper opening 414, lower opening 415 and a U-shaped opening 101 communicate with hole 116.

Preferably, a flange 718 extends inwardly near lower opening 415. Flange 178 preferably forms a substantially flat inner surface 720 which is preferably substantially perpendicular to longitudinal axis 107. Surface 720 may also be curved, and may be inclined at non-perpendicular angles. in relation to shaft 107.

Anchor member 106 preferably has a curved head 717 which is shaped and sized to fit into housing 710 and an internal space 815 of mandrel 714 (note that the upper part of curved head 717 is cut out in figure 7 to show mandrel 714). The curved head 717 may be substantially spherical or frusto-spherical and preferably has a recess 112 that is keyed to receive a hex wrench, torque wrench or other known driver to allow the anchor member 106 to be implanted by rotating, for example, a vertebra.

Figures 7B1-5 show various views of a jacket 612. Shirt 612 preferably has a U-shaped channel 610 for receiving the spinal rod 108 or some other fastener. Channel 610 is formed by struts 615a and 615b. The jacket 612 is generally cylindrical in shape, although other shapes are possible, and has a longitudinal bore 616. The struts 615a formed at the top of the jacket are flexible and preferably include retaining tabs 613a, b. Instead of two retaining tabs, one or more retaining tabs may be used. An upper opening 618 communicates with bore 616 and channel 610. The struts 615a form cylindrical walls or partial curves. The width of the U-shaped openings 610 in the upper aperture 618 formed by the outer edges of the curved wall of the struts 615a, b is preferably smaller than the diameter or width of the spinal rod 108 so that the rod flexes the struts by inserting into the sleeve and snapping into place. in place on the shirt. The upper inner surface 622 has a taper or inclination at the upper opening 618. The smaller opening 610 formed by the flexible struts allows the struts 615a, b to bend, compress and lock the rod when it is inserted into the U-shaped channel 610 of the sleeve 612. The conical upper inner surface 622 can facilitate spreading of the struts 615a, b.

A recess 625 is formed in the lower or base region 626 of the jacket 612. The outer surface 628 of the base region may be straight and generally cylindrical. The recess 625 communicates with the lower opening 630 and preferably with the bore 616. The recess forming interior walls 625 are preferably at least partially tapered, as shown in FIG. 7B1. The taper angle is preferably about 8 ° although other angles are contemplated. The recess 625 described below receives the mandrel 814.

The diameter of jacket 612 is preferably about 9 mm to about 10 mm, although other diameters are contemplated. The width or length of the openings 610 formed by the struts 615a, b at their smallest width is preferably about 5.9 mm (for a 6.0mm spinal rod), although other dimensions are contemplated. The height of jacket 612 is preferably about 9 mm to about 10 mm, although other dimensions are contemplated. Alternatively, the jacket 612B may be of other dimensions.

Figure 8 shows one embodiment of a mandrel 814. The mandrel preferably has slots 806 for creating resilient extensions 810 that can deflect outwardly to allow the anchor member head 717 to be inserted into the internal space 815 formed by the mandrel. Inner space 815 is formed by a hole 850 which communicates with the upper aperture 852 and lower aperture 854. Slots 806 may also have a circular shape radius 808 as a strain relief and to provide greater resilience to the extensions 810. Although the slits are shown extending from the lower end or base 812 into which the end 717 of the anchor member is inserted, the slots may alternatively extend from the upper end 820, or alternatively the slots 806 may extend from both the lower end 812 and the upper end 820. In one embodiment, the mandrel 814 may have a slot extending from the upper end 810 to the lower end 812 so that it may form a C ring. The arrangements, shapes and dimensions of the slots may alternatively differ from those shown. The lower aperture 854 is preferably sized to be smaller than the maximum diameter of the anchor member head 717. The inner space 815 preferably has a larger diameter than the lower aperture 854 to accommodate.

The mandrel 814 preferably has an externally tapered surface 822. The outer tapered surface 822 preferably is about 80 and preferably substantially conforms to the inner surface taper area 625 of the liner 612 to form what is sometimes referred to as a Morse Taper. The mandrel also has an inner surface 824 preferably shaped to substantially match the shape of the head 717. Preferably, the inner surface 824 is semi-spherically shaped to match the shape of the head 717, although the surface 824 may also be conical in shape or have other shapes. forms. Mandrel 814 is made of a resilient material, preferably titanium alloy, which can be compressed around head 717 to hold anchor member 106 securely in place. Preferably, the mandrel material is softer than the sleeve 612 and anchor member material 106. In one mandrel 814 embodiment, the upper inner diameter 816 is about 6.3mm and the height 818 is about 3.7mm. Alternatively, the mandrel 814 may be of other dimensions. In a preferred embodiment, the mandrel 814 may have a ring 826 which forms an extended shoulder 828 around the lower end 812. Preferably, the radius of the cutout 827 is formed on the outer surface where the tapered outer surface 822 meets the extended shoulder 828. The inner surface 830 (Figure 25) opposite the extended shoulder 828 is preferably flat and substantially perpendicular to the substantially flat lower surface 832, although the surface 830 may be curved and not perpendicular to the lower surface 832. The lower ring 826 preferably provides a larger surface area on the lower surface 832 to support the flange 718 formed near the lower opening 415 of the housing 710. Extended shoulder 828 may provide extra rigidity to the mandrel 814 and may better retain the bone anchor in housing 710.

The mandrel 814 is preferably inserted into the upper ends 114, or the U-shaped rod receiving channel 101, and is sized so that it can be inserted into the hole 116 of the upward anchor head 114, but is also sized and sized so that it fi nished at the lower end of the hole 116 of the anchor head. In other words, the diameter of the mandrel is such that it can pass through the upper apertures 414 of hole 116, but preferably cannot pass through the lower aperture 415 of hole 116. Alternatively, mandrel extensions 810 may be compressed to allow the mandrel to be inserted. in the lower aperture 415, and once within the anchor head 104, the extensions may expand. Thus, the mandrel can be inserted into the upper or lower opening of the anchor head. After the mandrel is inserted, the sleeve 612 may be inserted into the upper opening or the side through the U-shaped rod receiving channel 101 so that the lower end 626 of the sleeve is positioned around the upper end 820 of the mandrel. The liner 612 may be pressed downwardly until the retaining tabs 613a, b snap into the retaining slots 715a, b. Anchor member 106 may be inserted through lower opening 415 into hole 116. Mandrel 814 may then be inserted below hole 116 and snap-fitted to head 717 of anchor member 106. Alternatively, mandrel 814, or mandrel 814 and sleeve 712 may be inserted and positioned in the anchor head 104 and the anchor member head 717 inserted in the lower opening 414 and snapped into the mandrel. When the head 717 is inserted into the lower aperture 812 of the mandrel 814, the liner is positioned to allow the mandrel to expand so that the head can pass through the lower aperture 812 and then the mandrel detaches to retain the head 717 of the anchor member 106. .

If the spindle 814 with the extended shoulder 828 is used, the body or housing 710 preferably has a mounting notch 712, preferably formed in the lower part 118 of the housing 710. Preferably, the mounting notch is formed in the interior walls of the housing 710 between the flange 718 and jacket retaining slots 715a, b, although other locations for the mounting notch are contemplated. The mounting notch 712 allows the lower opening 854 of the mandrel 814 to expand while it is within hole 116 of housing 710 to allow the head of the anchor member to pass through the smaller opening 854 of mandrel 814.

In a preferred mounting method, the mandrel 814 is inserted into the upper opening 414 of the housing 710. The anchor domination head 717 is inserted through the lower opening 415 of the housing. With the expanded mandrel 828 of the mandrel aligned with the mounting groove 712 in the housing 710, the head 717 of the anchor member is inserted through the lower opening 854 of the mandrel. Since the lower aperture 854 is smaller than the head 717 of the bone anchor 106, the mandrel expands and the extended shoulder 828 is temporarily received in the slot 712 until the maximum diameter of the head 717 passes through the opening 854. As the head 717 is inserted further into the inner space 815, the extensions 810 retract and the extended shoulder 828 moves out of the mounting notch. Thereafter, the anchor member assembly 106 and the mandrel 814 move such that the extended shoulder 828 no longer aligns with the mounting notch 712 and the anchor member is retained by the mandrel such that the anchor member can be angled. and rotating with the mandrel, but cannot be released from the mandrel because the mandrel cannot expand sufficiently to allow the head 717 to pass through the lower opening854. Preferably, the mandrel and anchor member assembly moves apart so that the lower mandrel surface 832 contacts and is retained by flange 718 of housing 710.

With the mandrel and bone member assembly in the housing 710, the liner 612 may be inserted into the upper opening 424 of the downwardly moved housing so that the recess 625 receives and overlaps a portion of the mandrel 814. The liner is inserted into the housing 710 preferably such that retaining tabs 613a, b are received in the retaining slots 715a, b. In this manner, the jacket is retained in housing 710 and in turn retains mandrel 814 and anchor member 106 in housing. More preferably, the liner moves downwardly into housing 710 so that its inner tapered surface 622 overlaps the outer tapered surface 822 of mandrel 814 when retaining tabs 613a, b are received in retaining slots 710a, b. With the liner inserted, the anchor member may preferably still be angled and rotate polyaxially around the longitudinal axis 107 of housing 710.

Figure 7 further shows the locking cap 102 locked on the anchor head 104. The locking cap 102 preferably includes a main body or locking ring 900 (also shown in figure 9), an adjusting screw 1000 (also shown in figure 10) and one 1100 (also shown in figure 11). In one embodiment, the main body 900 preferably has an outer diameter 919, measured from tab 920a to tab 920b, of about 12.5 mm, and adjusting screw 1000 preferably has a height of 1018 of about 4.5 mm and preferably a outer diameter 1019 of about 7.0 mm. alternatively, the main body 900 and the set screw 1000 may be of other dimensions. Figures 13-14 show various views of saddle 1100. Alternatively, saddle1100 may be of other dimensions.

Figures 16-21 show various views of the locking cap 102. Set screw 1000 has outer threads 1023 which have internal threads 921 of main body 900. Advantageously, adjusting screw 1000 cannot be screwed out of main body 900 in the direction of the arrow. 1824 in figure 18 because of the enlarged portion 1925 at the base of the adjusting screw 1000. The adjusting screw 1000 is preferably preloaded on the main body 900 before the locking cap 102 is used on a bone anchor. More specifically, adjusting screw 1000 is rotated in the direction of arrow 1824 (FIG. 18) so that part 1925 engages the lower end 1926 of the internal threads of main body 900 and is tightened to create a friction fit.

The friction fit is such that it carries a certain predetermined torque ST applied to the adjusting screw to free the main body adjusting screw 900. Until the predetermined torque ST is applied, any rotational applied to the adjusting screw rotates the adjusting screw and main body. The torque for releasing the set screw may preferably be from about 2 to about 6 Newton-meters, and more preferably about 4.5 Newton-meters. In one embodiment, the set screw 1000 has a 1727 star type socket. Alternatively, the set screw 1000 may have other types of sockets or keyed recesses in other actuators or tools. Advantageously, as described in more detail below, a single drive tool or mechanism can actuate in one action both the main body 900 and the set screw 1000 simultaneously to lock the locking cap 102 in place on an anchor head and then continue. driving set screw 1000 alone until a rod inserted into the bone anchor and an anchor member are locked in place.

Saddle 1100 is preferably coupled to set screw 1000. That is, the adjusting screw 1000 is engaged with the upper part 1122 (see figure 11) of the saddle 11000, the upper part 1122 preferably being cylindrically shaped, and then the top of the part 1122 is slightly dilated to create a flange. More particularly, the upper part 1122 forms a rod 1130 which is fitted into a hole 1020 which communicates with recess 1727 in the set screw 1000.

After the upper part 1132 of the rod 1130 protrudes into recess 1727, the upper part where the wall was formed by depression 1137 is widened outward to engage saddle 1100 on adjusting screw 1000. The saddle is coupled to adjusting screw 1000, but it is free to rotate relative to set screw 1000 about an axis 1310 (see, for example, figure 19). Rod 1130 has a conical transition region 1135 where it joins at the bottom 2129. The lower aperture of hole 1020 has a tapered recess region to accommodate transition region 1135. Saddle 1100 has a recess 1320 which has a radius of curvature at around the same as the spinal stem.

The saddle 1100 preferably has helical notches 2130 in the lower portion 2129 (see Figure 21a) to improve rod grip. Preferably, the helical notches are inclined, similar to screw threads, and thus not perpendicular to the axis formed by recess 1320. are arranged in the direction of arrow 2135 (shown in figure 13A) from extension part 1142 to extension part 1144. The helical notches are preferably only slightly inclined and may provide greater grip force on the rod as they are slightly offset from the perpendicular to the axis. stem length.

The housing 710 has an upper end wall or upper surface 730 which preferably has one or more of the following recurs to assist in cooperating with the locking cap 102 to attach the locking cap to the bone member. Upper surface 730 (also referred to as end wall) may preferably have small holes 2730a, b formed by respective ramp surfaces 2735a, b and straight wall boundary surfaces 2737a, b. The upper surfaces 730 may also contain retaining surfaces 2738a, b as well as structures 733a, b. The outer edge 735 of the upper surface 730 may be chamfered or angled. Main body 900 may have projecting tabs 920a, b straight surface 925a, b. Protruding tabs 920a, b form bearing surfaces 930a, b. Preferably, the bearing surfaces 930a, b are substantially perpendicular to the straight surfaces 925a, b, although they may be non-perpendicular. The outer edge of the tabs 920 may also have a beveled or slanted surface. The main body 900 also preferably has flanges 3236 and 3238 and protruding surface 2632. Flanges 3236 and 3238 will interact with notches 2636 and 2638, respectively, formed in housing 710. The interaction of these housing structures with main body 90 will be described in more detail below. .

To lock (i.e. fasten) a rod and anchor member in a bony anchor, the locking cap 102 is positioned above the housing 710, as shown in figures 22-27. The locking cap 102 is particularly the flaps 920a, b are oriented relative to the small holes 2730a, b above the surface 730 of the housing 710, shown in figure 27. Preferably, the main body surface 2632 (see better in figure 26) extends slightly beyond surface 2634 of housing 710 when main body 900 is oriented in housing 710 as shown in figures 22-27. As such, the locking cap 102 is pressed down until it snaps into position, shown in figures 22-27. Note that the ramp surface 2642 in housing 710 and the ramp surface 2644 in main housing 900 facilitate this snapping action. That is, the ramp surfaces will interact to flex (e.g., elastically deform) the top of the housing so that the main body can snap into position. At this stage, the locking cap 102 is inserted into the anchor head and is in an open position not engaged or uncoupled.

Rod 108 is unlocked (i.e. detached); note the space 1108 between rod 108 and saddle 1100 in Fig. 24. In addition, anchor member 106 is also unlocked (i.e. detached); Note the gap 2508 between the housing 612 and the housing 710 in Figure 25. At this stage, the mandrel 814 is not axially compressed against the head of the anchor member 106, thus allowing the member 106 to rotate or angle axially as discussed above. Preferably, the saddle is inserted into the upper apertures 618 of the jacket when the locking cap 102 is inserted into the housing 710. More preferably, the dimensions of the saddle that fits into the opening 618 of the jacket are larger than the opening 618 in its natural state such that Saddle flex the struts 5615a, b outward. The conical upper inner surface 622 of the liner may facilitate spreading of the struts 615a, b.

The locking cap 102 is then preferably rotated about 90 ° (i.e. about 1/4 turn) in the direction of arrow 2731 (see figure 27). Note that the locking cover cannot be rotated in the opposite direction because structures 733a, b in housing 710 (see figures 7A and 27) make contact with tabs 920a, b in main body 900. As locking cap 102 is rotated in the direction of arrow 2731, resilient flexible tabs 920a, b find the small holes 2730a, b in housing 710 (see figure 27). The small holes 920a, b preferably have respective chamfered or crimped surfaces 2735a, b to facilitate movement of the tabs 920a, b upwards and over their small holes 273a, b in order to attach the locking cap in the closed position on the anchor head 104. main body900 has no cross-threadable screw threads during attachment of locking cap 102 to anchor head 104. Ramp surfaces 2737a, b of small holes 2735a, b are configured such that a predetermined RT torque is required for sliding and Deflect tabs 920a, b over the ramp surfaces. The predetermined RT torque required to slide and deflect tabs 920a, b over ramp surfaces is preferably less than the predetermined adjusting bolt ST torque (RT <ST) such that the torque applied to the adjusting bolt can rotate as much as the main body. together (ie locking cap) to the closed position. In this exemplary embodiment, a single instrument or tool applied to the adjusting screw may rotate the main body from open to closed position. The main body is rotated in the direction of arrow 2731 in Figure 27 until the tabs pass straight-walled surfaces 273 7a, b so that the tabs return to their non-flexed position and rest against recesses 2739a, b formed between limiting surfaces 2737a, b and retaining surfaces 273 8a, b.Preferably, the height of the tabs 920 is approximately the height of the small holes (e.g. straight wall limiting surface 2737) and the height of the retaining surface 2738 so that when the tabs 920 are in recesses 2739, the upper surface of the flap is approximately flush with the upper surface of the frames 733. Surfaces 2737a, b are preferably straight-walled such that if the locking cap is rotated in the opposite direction after sliding over the ramp surfaces, the respective flaps 920a, blow on the straight wall surfaces 273 7a, b in the closed position. Surfaces 273 7a, b thus act as restraints to prevent the locking cap 102 from turning backwards (to the open position) unless sufficient forces are applied. If the user continues to rotate the cap in direction 2710 (figure 27), the tabs 920a, b will contact the supporting surfaces 273 8a, b, and resist, and more preferably prevent further rotation of the main body 900.

Figures 28-33 show the locking cap 102 inserted into the anchor head and in the closed or seated or coupled position.

As shown in Fig. 32, flanges 3236 and 3238 in main body900 are positioned in corresponding notches 2636 and 2638 respectively in housing 710, and flange 3240 in housing 710 is positioned in a corresponding notch 3241 in main body 900. Oflange 3238 is preferably It has an inclined surface 3242 which tapers a diameter approximately equal to the inside diameter of the anchor head 104 to the maximum diameter shown in Figure 32. Flange 3238 may also have inclined surfaces 3222 and 3224 formed on its sides so that flange 3238 thickens. . Flange 3236 is preferably configured similarly to flange 3238. Inclined surfaces 3242,3222 and 3224 may facilitate flange 3238 to enter corresponding groove 2638. Preferably flange 3238 and notch 2638 are dovetail shaped as shown in area 3242 to prevent any expansion of the anchor head from occurring. More specifically, the projection or flange 3238 has an angled surface 3242a shown in figure 32 which corresponds to angled surface 3242b such that its outward force is applied to the anchor head 104, due, for example, to clamping forces as the rod is held in position, surface 3242a of flange 3238 would contact surface 3242b of flange 3240 and prevent anchor head 104 from expanding or expanding. Orient 2636 is preferably configured similar to notch 2638. At this stage, rod 108 is still unlocked; again, note the space between the rod 108 and the saddle 1100 in figure 30. Thus, as a comparison, figures 31 and 25 show that about 90 ° turn to set the locking cap 102 to the closed position not substantially or not at all. the positions of chisel 612 and chuck 814 have not changed at all. In this closed position, the flaps 920 that interact with the limiting surfaces 2737 prevent the interlocking cap from rotating to the open position while the interaction of the flanges 3236,3238 with the notches 3236, 3238 prevents the locking cap from being lifted out of housing 710.

Advantageously, the same drive tool or mechanism used to insert and close the locking cap 102 on the anchor head 104 can be used in a continuous action to further rotate the adjusting screw 1000. The main body and the adjusting screw rotate together until The main body is snapped into the closed position at which time the tabs 920a, b make contact with the structures 273 8a, b at the upper end 114 of the anchor head 104 of the bone anchor 100. As the tabs 920a, b make contact with 273 8a, b in anchor halter 104, the torque for turning the main body and adjusting screw increases until the applied torque is greater than the predetermined adjusting screw torque ST, at which point the frictional connection that holds the screw adjustment on the main body is exceeded and the adjusting screw continues to rotate alone regardless of the main body. The same tool can be advantageously used to move the adjusting screw down on the anchor head 104 to the locked position described below. Moreover, the same instrument used to loosen the main body adjusting screw, and which can also be used to Moving the adjusting screw down to the locked position of the rod where the rod is secured can also be used to swing the adjusting screw (ie, turning the adjusting screw in the opposite direction) until the enlarged threaded portion 1925 of the adjusting screw engages the adjusting screw. main body, at which time both the main body and the adjusting screw can rotate together. If sufficient force is applied to the opposite arrow direction 2731, the locking cover may return to open affix. Note that the torque required to overcome blockage of the widened thread part 1925 by the main body is preferably greater than the TT required for the flaps 920a, b to deflect on the straight wall surfaces 273 7a, b.

Optionally, the main body 900 may have an oppositely positioned pair of grooves where straight sections 925 of the main body 900 are located. Straight section 925 or grooved cutouts can be used with a different tool to alternatively drive main body 900. However, such a tool cannot also set set screw 1000.

Figures 34-38 show the locking cap 102 inserted into the anchor head 104, and the adjusting screw 1000 driven low on the anchor head 104 to lock the rod 108 in place. As the adjusting screw 1000 is depressed downwardly, it presses the saddle 1100 against the rod 108 to press the rod to the bottom of the jacket 612.

Note the lack of space between saddle 1100 and rod 108 in figure 36. As the adjusting bolt is driven further down, the saddle pushes the rod further down, causing the sleeve 612 to move. downwardly by compressing the chuck 814 against the head of the anchor member 106, locking the anchor member in place. More preferably, the liner 612 moves downwardly into the housing body 710 such that its inner tapered surface interacts with the tapered outer surface of the mandrel 814 so that the resilient mandrel extensions are compressed inward to lock the anchor member in position so that the anchor member is fixed to the body 710. The adjusting screw 1000 may be depressed down until the lower surface 2512 of the sleeve 612 abuts the lower inner surface 718 of the housing 710, or until the lower surface 2512 abuts the shoulder 828. spindle (shown in figure 37). The anchor can also be configured so that the underside surface 2512 of the sleeve cannot rest on either the housing or the mandrel when the anchor member is in the locked position. Additionally, or alternatively, retaining tabs 613a, b may be supported on respective lower edges 3015a, b of slots 715a, b upon completion of the anchor member locking process (shown in Figure 36). Note that the stem and anchor member locking process (that is, the operation of removing the adjusting screw once it is free of the main body so that the saddle contacts the stem) has little or no effect on the relative closed positions. main body 900 and housing 710, as shown in comparison of figures 32 and 38.

A further illustrative method of using the bone fixation system using bone anchor 100 is described below. Bone anchor 100including the anchor member and assembled body (including the mandrel sleeve, but preferably without the locking cap) is attached to the bone.

At this stage, the anchor member 106 may preferably pivot or angularly rotate relative to the housing 710. The anchor member 106 may be provisionally locked relative to the housing 710 by applying a force to move the jacket 612 downwardly to the lower opening 415 to compress the housing. mandrel 814 against head 717 to prevent further movement of the anchor relative to housing 710. This temporary locking can be done before or after the spinal rod is placed in the housing and can be done before the locking cap is attached to the housing or the spinal rod is secured to the housing. In one method, the spinal rod may be placed on the jacket and used to apply pressure on the shirt to lock the anchor member in the housing prior to and independently of locking the spinal rod. With the anchor member locked in the housing 710, the spinal rod may move in or removed from the housing 710 (translated, rotated). The spinal rod can then be secured to the housing using the locking cap 102 in the manner described above.

Note that the locking cap is not limited to use on polyaxial bone anchors. Figures 39 and 40 show alternate bone anchors which may employ the locking cap of figures 7 and 9-11. Bone anchor 3900 is an example of a monoaxial bone anchor having an anchor 3906. Bone anchor 4000 has anchor member 4006. , which is an example of a hook that can engage the spinous process, a blade or other bone.

Figures 2 and 3 illustrate tool engaging surface 140 and 150 on the outside of anchor head 104 which may be used as a retention and manipulation tool to assist in the implantation process.

A first illustrative method of fixing the spine will be described. The method described below may be performed using any of the above-described bone anchors, or any other bone anchors known in the art, although polyaxial and monoaxia-superscript bone anchors are preferred. The method generally includes attaching a first bone anchor 100 to one vertebra, preferably attaching a second bone anchor 100 to another vertebra, and securing the spinal shaft to the first and second bone anchors 100 to align the vertebrae. This can be obtained, for example, by inserting anchor member 106 of the first bone anchor 100 in a first vertebra is found. The second bone anchor100 may alternatively be implanted in one or more vertebrae in other regions of the spine (ie cervical, thoracic or lumbar region). In order to insert anchor member 106 into the vertebra, it may be necessary to insert anchor member 106 into an orientation between about 0 'and about 250 medially or laterally, and more preferably between about 0' and about 15 medially or laterally.

Additionally, or alternatively, it may be necessary to insert the anchor member 106 in an orientation between about 30 and about 50 to above, and between about 30 and about 40 upwards. The above-described polypolyxeal bone anchors may be configured and sized to provide the necessary mediated or lateral and / or upward angulation, although the present method is not limited to the described polyaxiaisaqui bone anchor structures.

Prior to inserting the anchor member 106, it may be desirable to drill and / or drill a hole in the vertebrae. In the event that the hole is opened, it may be preferable not to open the anterior cortex of the vertebra. Anchor head 104 and curved head 717 may preferably be pre-assembled before anchor member 106 is inserted into vertebrae. Alternatively, once the anchor member 106 has been completely inserted into the first vertebrae, the anchor head 104 may be snapped into the curved head 717 of the anchor member 106.

The second polyaxial anchor 100 is preferably attached to an adjacent vertebra, or another vertebra, for example by threading anchor member 106 (which in this case is a screw) to the vertebra.

Alternatively, the second polyaxial anchor 100 may be attached to other vertebrae including those in the cervical, thoracic and lumbar regions. Once the second polyaxial anchor is deployed, the first and second anchor heads 104 may be rotated to align their respective rod receiving channels so that a spinal rod 108 can be inserted.

Once the vertebrae have been repositioned to correct near deformity, the respective locking caps 102 of the first and second polyaxial bone anchors 100 may be tightened to secure the spinal shaft 108 to the first and second polyaxial bone anchors 100, to secure the angular positions of the anchor heads. 104 with respect to the anchor members 106, thereby forming a substantially rigid construction.

Alternatively, one end of the spinal rod 108 may be inserted into one of the anchor heads 104, and the spinal rod 108 manipulated to reposition the vertebral bodies. Then, the other end of the spinal rod 108 may be inserted into the other of the anchor heads 104 and then the spinal rod 108 fixed in position. The first end of the spinal rod 108 may be secured to one of the anchor heads 104 with the locking cap before the spinal rod 108 is manipulated to reposition the vertebral bodies. Also in another embodiment of this method, bone anchors 100 may be inserted into the spine in the above manner, both ends of the spinal rod108 may be inserted into the anchors 100, and one end of the spinal rod fixed or attached to the anchor 100 and an applied distraction or compression force for moving the polyaxial anchor along the spinal shaft 108 to apply both a distracting and compressive force, and then securing the second end of the spinal shaft 108 to the bone anchor.

Once the first and second polyaxial anchors 100 have been implanted, their anchor heads 104 may rotate to align their respective rod receiving channels so that a spinal rod 108 may be inserted into it. Once the vertebrae have been repositioned to correct the near deformity, the locking caps can be tightened to secure the spinal rod 108 to the first and second polyaxial anchors 100, and to fix the angular positions of the anchor heads 104 relative to the anchor member 106, forming thus a substantially rigid construction.

Although it is apparent that the illustrative embodiments of the invention disclosed herein meet the above stated objectives, it is apparent that numerous modifications and other embodiments may be conceived by those skilled in the art. Features and structures, such as, for example, the locking cap, may be used singly or in combination with other features and structures. Therefore, it is understood that the appended claims should cover all such modifications and embodiments that fall within the spirit and scope of the invention.

Claims (25)

Bone anchor for attaching a fixture to a bone, comprising: an anchor member having a bone socket and a head for attachment to the bone, an anchor head having an upper, lower and lower part; a hollow inner space extending from the top to the bottom, the head portion of the anchor member being inserted into the hollow inner space of the anchor head so that the epoleaxially rotatable anchor member relative to the anchor head, the anchor head including a generally U-shaped opening for receiving the fastening element; A locking cap including a main body and an adjusting bolt, the main body releasably engaging with the top of the anchor head, the adjusting bolt being snap-fitted to the main body in a preloaded condition, a predetermined torque being applied in a first direction for the adjusting screw relative to the main body to turn the adjusting screw relative to the main body of the preloaded condition for free condition. Bone anchor according to Claim 1, characterized in that the main body of the locking cap is secured to the upper part of the anchor head by rotating the main body approximately ninety degrees (90 °) relative to the anchor head. , the main body being rotated from an open position to a closed position. Bone anchor according to claim 2, characterized in that the main body of the locking cap includes at least one resiliently defectable tab extending therefrom and the anchor including at least one cavity in its upper surface, the deflecting tab. over at least one cavity during rotation of the main body in the first direction relative to the anchor head of the open position to the closed position. Bone anchor according to claim 3, characterized in that at least one cavity includes a limiting surface, the limiting surface resisting rotation of the main body relative to the anchor head in a second direction opposite to the first direction, when the main body is in the closed position. Bone anchor according to claim 4, characterized in that the upper surface of the anchor head additionally includes a retaining surface, the limiting surface and the retaining surface defining a recess, the flap being located neccessary when the main body is located. in the closed position. Bone anchor according to claim 1, characterized in that it further comprises a compressible mandrel having a lower surface supporting a lower flange at the lower part of the anchor head. Bone anchor according to claim 6, characterized in that the fastening element is a spinal rod having an outer diameter and a bone anchor which additionally comprises a glove having a U-shaped channel, the glove including opposite braces defining at least one. at least a portion of the U-shaped channel, the struts being flexible and defining a width between them at a larger aperture, the width being less than the outside diameter of the spinal rod so that the spinal rod is snapped into the sleeve during insertion of the rod in the U-shaped channel. Bone anchor according to claim 7, characterized in that the glove has an internal recess that receives at least a portion of a mandrel mounted therein, including a internally tapered surface, the mandrel including an externally tapered surface; the internally tapered sleeve surface providing a compressive force on the externally tapered mandrel surface in a locked position. Bone anchor according to Claim 6, characterized in that the anchor head has a mounting groove facing the hollow inner space and the mandrel has an extended shoulder, the mounting groove receiving the shoulder extended therein when the mandrel is located. in the hollow inner space while the anchor member head portion is inserted into the inner space of the mandrel. Bone anchor according to claim 1, characterized in that the locking cap includes a saddle coupled to the adjusting screw, the saddle being rotatable relative to the adjusting screw, the saddle including a curved recess with notches for adherence. of the fastener in a locked position. Bone anchor according to Claim 1, characterized in that the main body includes inner threads and the adjusting screw includes outer threads that mates with the inner thread of the main body, the adjusting screw further including an enlarged part at a lower end. It fits the lower end of the threaded main body in a preloaded condition. Bone anchor according to claim 1, characterized in that the adjusting screw includes an enlarged portion at a lower end that engages the main body in a pre-loaded condition, the enlarged portion generally preventing rotation of the adjusting screw relative to to the main body in a second direction, opposite the first direction, in a preloaded condition. Bone anchor according to claim 1, characterized in that the anchor head, main body and adjusting screw include upper surfaces, the upper surfaces of the anchor head, main body and adjusting screw being generally planar in a closed position and a locked position, the upper surface of the adjusting screw being spaced from the upper surface of the main body in a preloaded condition. Bone anchor according to Claim 1, characterized in that the adjusting screw includes external threads and an enlarged part at a lower end, and the main body including internal threads that engage with the external threads of the adjusting screw. adjusting screw in a first direction by causing the main body to rotate with the adjusting screw until the predetermined torque is applied to the adjusting screw relative to the main body, the enlarged portion engaging a lower end of the main body in a preloaded condition. Bone anchor according to claim 14, characterized in that the predetermined torque is about 2 Newton-meters to about 6 Newton-meters. Bone anchor according to claim 14, characterized in that the required torque applied to the locking cap to rotate the locking cap from the open position to the closed position relative to the anchor head is less than the predetermined torque. Bone anchor according to claim 16, characterized in that the locking cap includes a main body and an adjusting screw, the adjusting screw being threadedly engaged with the main body, the limiting surface and the inclined surface of the lid. lock being located on the main body. 18. Bone anchor for engaging a vertebrae fastener comprising: an anchor member for engaging a vertebra, an anchor head having an upper and lower part, the anchor head having a general shape tubular having an inner cavity, an upper opening in the upper part communicating with the inner cavity and a lower opening in the lower part communicating with the inner cavity, the upper part having an end wall, at least one notch located near the upper opening, a U-shaped opening formed in the anchor head for receiving the fastening element, the end wall including at least one cavity formed therein; A locking cap comprising a main body and an adjusting screw, the main body including at least one flexible flap and at least one flange, the at least one deflectable flap interacting with at least one cavity so that the at least one flap is deflected while the The main body is rotated in a first direction with respect to the anchor head from the open to the closed position by calling at least one flange positioned in at least one notch in the provisionally closed position retaining the fastener within the U-shaped opening, the cavity resistant to rotation of the main body in a Bone anchor according to claim 18, characterized in that at least one cavity includes an inclined surface and a limiting surface, the inclined surface being inclined with respect to the end wall and the limiting surface extending substantially perpendicular to the end wall. Bone anchor according to claim 19, characterized in that the end wall further includes an inclined surface and a limiting surface, the inclined surface and the defined limiting surface a recess, at least one deflectable flap located in the recess when the body main position is in the closed position, the locking cap being rotated approximately 90 degrees relative to the anchor head from the open to the closed position to position at least one deflectable tab in the recess. Bone anchor according to Claim 18, characterized in that the at least one dovetail-shaped flange and the at least one dovetail-shaped notch has the dovetail-shaped flange and the dovetail-shaped notch limiting the top of the anchor head to expand beyond a predetermined distance when the locking cap is mounted to the anchor head in the closed position, the flange and dovetail notch resisting movement of the locking cap along a longitudinal axis of the anchor head in the closed position. 22. Bone anchor for engaging a bone anchor comprising: an anchor member having a bone engaging portion and a head for attachment to the bone, an anchor head having an upper, lower portion and a hollow inner space extending from the top to the bottom, the head part of the anchor member being inserted into the hollow inner space of the anchor head, the top part of the anchor head including a generally U-shaped opening to receive the element defixation, a longitudinal axis and a limiting surface facing hollow internal cavity near the top, the limiting surface is located at a first distance from the longitudinal axis; a locking cover removably fitted to the upper part of the anchor head, the locking cover including a limiting surface located at a second distance from the longitudinal axis in an open position, the second distance being greater than the first distance, the limiting surfaces of the anchor and locking cap facilitating snap locking of the locking cap relative to the anchor head, while the locking cap engages with the anchor head in the closed position. Bone anchor according to claim 22, characterized in that the locking cap includes an inclined surface near a lower end and the anchor head including an inclined surface near the top, the inclined surfaces of the locking cap and the locking surface. anchor head making it easy to close by locking the locking cap into the anchor head. 24. A combination of a bone anchor and a fixation element for holding adjacent vertebrae, characterized in that it comprises: an anchor member for mounting the vertebra, the anchor member having a bone socket and a head, an anchor head having a lower part, an upper part and a longitudinal axis, the upper part including an end wall, the anchor head coupled to the near lower anchor member, the anchor head including a hollow inner space and a generally U-shaped opening for securing member; a sleeve positioned within the hollow inner space, including the opposing struts defining at least a portion of the U-shaped channel, the struts being flexible and defining a width therebetween at a larger opening, the width being less than that the outside diameter of the spinal shaft so that the spinal shaft is snapped into the glove during insertion of the shaft the U-shaped channel and the U-shaped opening; A locking cap removably mounted to the upper part of the anchor head, the locking cap blocking movement of the fastener outside the anchor head along the longitudinal axis when the locking cap is in the closed position. 25. A method of mounting a bone anchor from a spinal fixation device including a fixture, a bone anchor including an anchor member having a bony fitting portion and a head, an anchor head having an upper opening, a lower opening and a hollow inner space in communication with the upper and lower openings and a mounting slot facing the inner space and a mandrel having an inner space, a lower opening in communication with the inner space, a lower opening shoulder and an upper end, the method characterized it comprises: a) inserting the head part of the anchor member through the lower anchor head opening into the inner cavity, b) aligning the mandrel shoulder with the notch of the anchor head assembly, c) inserting the head part anchor member through the lower mandrel opening while the mandrel is located in the the anchor and shoulder are aligned with the mounting notch so that the lower mandrel opening expands, pushing the mandrel shoulder into the mounting notch, d) pushing the head portion into the inner space so that the lower mandrel opening opens retract to a natural state and the shoulder moves out of the mounting notch, the head portion of the anchor member being retained within the internal space between the upper end and the lower mandrel opening; ee) propelling the mandrel and the anchor member toward the lower opening of the anchor head so that the mandrel shoulder is positioned near the lower opening of the anchor head.